You can now use Google Voice with Twitter’s two-factor authentication service. Last May 22, Twitter pulled the curtain down to reveal the feature as the solution to the string of malicious hacking incidents on high-profile accounts.

Similar to the ones employed on ATM machines, the two-factor authentication lets Twitter users to sign in using a code, apart from the usual username and password. This prevents hackers to invade an account with the use of a keylogging spyware. The Twitter login verification can be activated in the Privacy Settings tab. Once activated, Twitter will send you a six-character code via SMS that you will enter to fully login.
Every day, a growing number of people log in to Twitter. Usually these login attempts come from the genuine account owners, but we occasionally hear from people whose accounts have been compromised by email phishing schemes or a breach of password data elsewhere on the web,” says Twitter on a blog.
However, social media users consider the absence of a phone a big risk in using the two-factor authentication. This usually happens when the phone is drained or is incapable of having a signal. Moreover, there are establishments who use a single account but don’t share a single phone. These mishaps are answered by Google Voice.
By running a Google Voice account, users can access messages and answer calls on a different device. Users can gain access to authentication codes even with the absence of a mobile device, provided they have a connection to the Internet and to their Google Voice account. Routing of Google emails and messages to an alternate device is also an option. This means that groups, especially colleagues, can now share a single Twitter account by getting the same SMS message bearing the authentication code.

 
SOURCES:
http://news.cnet.com/8301-1023_3-57585752-93/twitter-fights-hacking-with-two-factor-authentication/
https://blog.twitter.com/2013/getting-started-login-verification